The invention relates to an apparatus for detecting ultrasound images from a body under examination, which apparatus comprises a first unit emitting ultrasound pulses comprising one or more electroacoustic transducers and a first unit receiving ultrasound pulses comprising one or more electroacoustic transducers, said first emitting unit and said first receiving unit being faced each other and being spaced apart from each other by a predetermined distance such that they are arranged at opposite sides of a cavity housing said body under examination and the ultrasound pulses emitted from said first emitting unit are received by said first receiving unit after passing through the body under examination and are transformed into transmission signals, a control unit for said first emitting unit, a unit processing the received signals, image generating means and displaying means for said images, said processing unit comprising a unit evaluating the attenuation of ultrasound pulses and/or the propagation speed of ultrasound pulses.
The operation of such type of apparatuses is usually called as transmission mode, in which only the wave that has passed through the body is examined without considering the reflected echoes and by means of which it is possible to evaluate the propagation speed of ultrasound pulses when the ultrasound beam passes through the body under examination and the attenuation due to the structures of the body under examination.
It is also possible to use the transmission mode in combination with the reflection mode, by means of which it is possible to generate images by means of the echoes generated from the structures of the body under examination in response to the ultrasound beam transmitted to said body under examination.
Such technology can be used particularly in breast ultrasound imaging.
Apparatuses of this type are described in documents U.S. Pat. No. 7,699,783 and U.S. Pat. No. 7,771,360, which content is to be considered as a part of the present description.
In particular three types of images are produced by using the two different modes: images that represent maps of the propagation speed of ultrasound pulses and attenuation of ultrasound pulses of tissues for each point of the body under examination are generated by the transmission mode, while by the reflection mode tomographic images are generated.
Information about propagation speed of ultrasound pulses can be used for spatially correcting the geometric deformations in tomographic images due to tissues being heterogeneous.
As regards ultrasound imaging a widely used and increasingly developing method is the use of contrast agents, typically microbubbles that have a non-linear reflection behaviour and therefore that generate echoes with frequencies corresponding to fundamental frequency harmonics of the emission pulses transmitted to the body under examination.
The use of contrast agents is typically useful for investigating properties or conditions of blood flow and/or the condition of tissue vascularization.
There is a rising attention in using the so called “targeted” contrast agents, wherein microbubbles are associated to ligands that bind to receptors characteristic of specific diseases, causing contrast agents to gather in the areas affected by the disease.
In the known apparatuses described above there is the unsolved problem of recognizing the second harmonic signal components actually due to contrast agents, since the harmonic generation can be due to the non-linearity in scattering and propagation of ultrasounds in tissues.
This leads to the uncertainty in interpreting information obtained from imaging with contrast agents, while on the contrary the need of having reliable systems for recognizing the presence of contrast agents increases both in the analysis of blood flows according to the different modes and/or for several diagnostic purposes.
The present invention aims at solving the problems mentioned above by an apparatus as described hereinbefore and wherein in addition said processing unit comprises a unit comparing said values of propagation speed of ultrasound pulses and/or of the attenuation of ultrasound pulses with predetermined threshold values, the transmission signals resulting from the presence of contrast agents within the body under examination when the comparison of said attenuation of ultrasound pulses and/or of said propagation speed of ultrasound pulses has a specific difference with respect to the corresponding threshold value.
Depending on the type of contrast agent and of the tissue under examination, the values of the attenuation of ultrasound pulses or of the propagation speed of ultrasound pulses under the presence of contrast agents to be considered as indicating the presence of such contrast agents, can be under or over said threshold values.
Experimental studies have shown that, in the transmission ultrasound mode by means of which it is possible to obtain information about the propagation speed of ultrasound pulses and attenuation of ultrasound pulses, the presence of contrast agents can significantly affect the values of the propagation speed of ultrasound pulses and in particular of the attenuation of ultrasound pulses.